Burners are widely used in the iron and steel industry, and are used especially in melting processes for the production of steel or other metals, such as in electric arc furnaces (EAF) for heating and melting metal, to increase the productivity of the process and to reduce the consumption of electricity. They are used particularly on rolling lines in furnaces for continuous heating of the molten product. Another particular use of burners is in pre-heating systems for system components, such as ladles, tundishes, etc. But today burners are also used in other fields, including the incineration of solid urban waste.
EAF in which burners are used often suffer from restrictions due to the poor distribution of heat created by traditional burners. A type of burner which is commonly used in EAF is the concentrated flame burner, which offers a poor mixing capacity and oxidises scrap. Observation shows the presence of large quantities of methane and free oxygen in the furnace, reaching a considerable distance from the burner head.
Traditional burners have large portions of free oxygen in the flame and this feature, together with the localised heating effect of the burner on the scrap makes them perfect for oxygen cutting of scrap, but not for evenly distributed heating. The oxidisation of the scrap causes serious disturbance to the overall energy balance of the melting process.
The concentration of the flame produced by these burners causes other disadvantages. The volume of scrap heated remains limited, while there is often perforation in the scrap up to the electric arc area, disturbing the arc and causing combust gas to rise up the electrode without passing through the scrap, which is not efficiently heated. Moreover, the ring of scrap at the base of the column in the furnace is pre-heated discontinuously meaning that a higher number of burners have to be installed in the furnace.
A burner of this kind is disclosed in document FR-A-1438494, whereby a concentrated flame is produced by the burner head so that the flame envelope has the shape of an annulus. This burner produces thus a heat concentration in a narrow cylindrical volume in front of the burner. From using this burner it ensues that the heat produced is not efficiently used during the whole stage of scrap melting.